Need help setting up Google Play Services for my game.

I've always had a difficult time trying to get Google Play Services to work on an Android build of my Unity projects. Current it looks like it's trying to login, but it ends up failing and not getting the player logged in. The main guide on Google Play's plugin page doesn't help out much other than the very basics of setting it up. I've followed all the steps on the page as well and it still won't login my game. If someone can give me an up to date guide on how to setup Google Play properly in Unity that'd be good. Heck, I'd even get someone from Fiverr to help me out at this point. Am I the only one who's never gotten Google Play to work right in Unity?